1. Field of the Invention
The present invention relates to an information storage device, and more particularly, to an information storage device using movement of a magnetic domain wall, and methods of manufacturing and operating the information storage device.
2. Description of the Related Art
A general hard disk drive (HDD) is a device that reads and writes information by rotating a magnetic recording medium in a disk form and moving a reading/writing head along the magnetic recording medium. HDDs are non-volatile data storage devices capable of storing data of 100 gigabytes (GB) or more and are used mostly as a main storage device in computers.
However, a HDD includes a lot of moving mechanic systems. These mechanic systems may cause various mechanic faults when the HDD is moved from one location to another location, or affected by shock, thereby decreasing mobility and reliability of the HDD. Also, these mechanic systems increase the complexity and costs of the manufacture of the HDD, increase the power consumption, and generate noise. In particular, the increased complexity and costs of manufacturing HDDs become more serious when the HDDs are minimized.
Thus, recently, a research to provide a new storage device, which does not include moving mechanism systems, but allows a storage of information as large as a HDD, is under progress. As an example, a data storage device using the moving principle of a magnetic domain wall moving in a magnetic material has been suggested.
Magnetic minute regions constituting a magnetic body are called magnetic domains. In a magnetic domain, the direction of the magnetic moment is identical. The size and the magnetization direction of the magnetic domains and the direction of the magnetization can be appropriately controlled by varying or controlling the property, shape and size of the magnetic material, and external energy. A magnetic domain wall is a boundary between neighboring magnetic domains each having different magnetization directions, and can be moved by a current or a magnetic field applied to the magnetic material. When the principle of movement of the magnetic domain wall is applied to an information storage device, it is possible to move the magnetic domains to pass through fixed reading/writing heads in a controlled manner by the movement or propagation of the magnetic domain wall, and thus data can be read/written without the rotation of the recording medium. The information storage device employing the principle of movement of the magnetic domain wall can store a large amount of data and at the same time does not include moving mechanical systems, thereby avoiding disadvantages associated with the moving mechanical systems. Thus, such storage device may have an excellent mobility and reliability, can easily be manufactured, and consumes less power.
However, information storage devices using movements of the magnetic domain wall are still at the initial stages of research and further research and developments are needed in order to put them into practical use.
The conventional writing method can be divided into a method using an external magnetic field and a method using spin torque of electrons. The writing method using an external magnetic field cannot is not applicable to a magnetic layer storage medium which has a high magnetic anisotropic energy. When a soft magnetic layer such as a NiFe layer is used as a storage medium, it is difficult to secure stability of the movement of the magnetic domain wall and to realize high recording density. Meanwhile, the method using spin torque of electrons cannot be applied to a magnetic layer which has a thickness of greater than about 3 nm. Thus, the writing method using the spin torque of the electrons cannot be applied to a perpendicular magnetic recording storage device which requires a magnetic layer having a thickness of about 100 nm or greater.